1. Field of the Invention
This invention relates to a batch-type mixer for agitating and/or mixing two or more powdered to particulate materials with one another or one or more powdered to particulate materials and a liquid with one another at an elevated speed and occasionally with moderate suppression of the crushing action.
2. Disclosure of the Prior Art
The mixing systems for powdered to particulate materials include a mixed system employing a mixer with a revolving vessel, and a batch- or continuous type mixer with a fixed vessel. For agitating and/or mixing powdered to particulate materials at an elevated speed, a high-speed batch type mixer with a fixed vessel is preferentially employed.
With the high-speed mixer, one or more kinds of powdered to particulate materials to be mixed together are injected in predetermined amounts into a fixed vessel and the agitating blades of various profiles mounted in the vessel are revolved at an elevated speed of the order of 500 to 10,000 rpm to fluidize and agitate the materials compulsorily to effect the mixing. This high speed mixer may be typified by a Henschel mixer, a high-speed mixer or a fine mixer.
It is required of the high speed mixer to elevate the mixing degree. The powdered to particulate materials may be classified into those having finer particle size, referred to hereafter as the powders or fine powders, or powdered or finely powdered materials, and those having coarser particle size, referred to hereafter as the particulate materials. The powdered and finely powdered materials tend to be flocculated and, when they are mixed in the flocculated state, the mixing degree is lowered.
In the above described high-speed mixer, the powders are fluidized and mixed together in the flocculated or lumped stated so that the mixing degree is lowered.
In order to obviate this deficiency, there is proposed a mixer 90, known as the MGT mixer, in which, as shown in FIG. 10, cracking means 92 having multi-stage blades 93 adapted to be revolved at elevated speeds in a box-shaped casing 91 is separately provided at the lateral side of the casing in such a manner that the flocculated powders may be cracked simultaneously during mixing of the powdered to particulate materials.
In this mixer, since the cracking is performed simultaneously with mixing of the powdered to particulate materials, powders X an Y exist in the vicinity of the multi-stage blades of the crushing means, such that the flocculated powders X can not be cracked efficiently. Above all, with the higher mixing ratio of the powders Y, the powders X are less likely to impinge on the multi-stage blades and hence can be cracked only with considerable difficulties.
It becomes therefore necessary to crack the flocculated powders X before mixing the powders X and Y together.
On the other hand, when the powdered to particulate materials are mixed in the above described mixer, some materials undergo changes in the properties indigenous to them due to cracking in the course of mixing. Above all, the particulate materials, such as the granulated sugar having a particle size ranging between about 350 and 800 microns, are crushed by the agitating blades rotating at an elevated speed such that the properties indigenous to the materials are altered.
Although the number of revolutions of the agitating blades can be lowered to the extent that the particulated materials are not crushed in this manner, the mixing speed is then lowered undesirably.